Embodiments described below relate to process control devices. In particular, the embodiments relate to flow meters used in process environments.
In process control environments, it is advantageous to monitor the amount of fluids passing through various conduits within the process system. Various techniques have been developed to measure the flow rates including mechanical flow meters, pressure based meters, optical flow meters, vortex flow meters, electromagnetic flow meters, ultrasonic flow meters, and Coriolis flow meters, for example.
Mechanical flow meters place physical elements in the fluid stream that move in response to the fluid flow. One example of a mechanical flow meter is the turbine flow meter, in which a turbine rotor is set in the path of a fluid stream which imparts a force on the blade surfaces of the rotor to cause the turbine to rotate. The speed at which the rotor rotates indicates the velocity of the fluid flow.
In vortex meters, a bluff body is introduced into the fluid flow and the frequency at which vortices are formed behind the bluff body is used as a measure of the fluid flow. In some vortex meters, the vortices are measured using pressure sensors that measure pressure changes associated with vortices.
In ultrasonic meters, an ultrasonic signal is passed through the conduit in both an upstream and downstream direction through the fluid flow. The difference in the speed at which the ultrasonic signal passes upstream versus downstream is used to calculate the fluid flow.
In pressure based meters, the pressure along one or more points within the conduit is used to determine the flow rate of the fluid. Many pressure-based meters introduce a constriction in the fluid flow and sense the pressure before the constriction and the pressure after or within the constriction. One example of a pressure-based meter utilizes an orifice plate with a hole, or a plurality of holes through it. In such meters, a differential pressure sensor is used that senses the difference in the pressure before and after the orifice plate.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.